| myersport |
Posted
Saturday, Mar 11th 9:27pm [Edit] [Quote] [IMS] [View car] |
Member
Post nr. 184
east tennessee
'82 320iS. '91 327iC |
I dyno'd my car today, just to see where I'm at. First, a quick refresher:
-1988 supereta engine (8.5:1 comp)
-1991 stock 325i valvetrain and 1.3 motronic
-Custom chip
-Stock 323i exhaust and manifolds
-Inexpensive cone air filter
This is mild 2.7 conversion, with the exception of the chip and air filter these are all off-the-shelf BMW parts.
The results at the rear wheels:
-142 hp at 5200 rpm
-171 lb-ft torque at 3600 rpm
Factoring the common 16% drivetrain loss shows approximately
-163 hp
-198 lb-ft
Not astronomical numbers, but they make for a highly competent daily driver!! These will just give you guys building strokers out there a baseline, as high comp pistons, aggresive cams, high dollar head work, megasquirt, etc. will obviously go up from here. This run was done on a Mustang dyno, which I have heard tend to err on the conservative side.
--Dennis
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| RDAvena |
Posted
Saturday, Mar 11th 9:37pm [Edit] [Quote] [IMS] [View car] |
Staff
Post nr. 1600
SELECT * FROM users WHERE clue > 0
1981 323i, 1988 545is, 1997 528i |
nice numbers.
guess some of the others in the community have been using optimistic dynos. Some have claimed 200 crank HP. Still plenty of umph over the 2.3. |
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| imaradiostar |
Posted
Monday, Mar 13th 5:53am [Edit] [Quote] [IMS] [View car] |
Member
Post nr. 671
Nashville, TN
81 323i, 82 525i, 85 524td, 90 535i |
Looks good. Don't suppose you have the numbers from an E30 325i as a comparison?
Any plans to upgrade from there?
My little engine probably doesn't perform as well as yours and it's plenty powerful...so I certainly understand if you don't plan to mess with it!
I still have the urge to turbocharge my stroker. I also have another NA engine in the works and I'm debating which one to work on first. No matter how you slice it things end up costing money!
jamie
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| Tricord |
Posted
Monday, Mar 13th 12:17pm [Edit] [Quote] [IMS] [View car] |
Administrator
Post nr. 929
Belgium, Europe
323i Baur |
I wonder how the supereta (8.5:1 cr, better flow) compares to the regular eta (11.0:1 cr, worse flow) using stock parts like we did.
My version has breathing problems above 5000rpm, but it sure hauls under that rpm limit. I reckon I have steeper power and torque curves, but they plummet at 5000rpm instead of the usual 6000. I think I must be getting about 160HP at the crank, but no time or money to put the car on a dyno and find out the details.. |
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| RDAvena |
Posted
Monday, Mar 13th 4:02pm [Edit] [Quote] [IMS] [View car] |
Staff
Post nr. 1605
SELECT * FROM users WHERE clue > 0
1981 323i, 1988 545is, 1997 528i |
| Tricord wrote: | I wonder how the supereta (8.5:1 cr, better flow) compares to the regular eta (11.0:1 cr, worse flow) using stock parts like we did.
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My thoughts are less power due to the lower compression. You have the added benefit of the eta torque down low but the compression is not helping make power past 5000. |
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| Madhatter |
Posted
Monday, Mar 13th 4:31pm [Edit] [Quote] [IMS] [View car] |
Member
Post nr. 20
Australia - QLD
E21, E24, E30 |
depending on your dyno (and just how competent the operator is), the loss figure is significantly higher than 16%, low 20's is a more realistic figure, more if you run an auto.
Compression ratio isnt going to produce large power increases, at best you are talking 1.5-2% as a maximum per full point increase in comp ratio. Its not as important as some people think. |
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| Gabi_323i |
Posted
Monday, Mar 13th 10:12pm [Edit] [Quote] [IMS] [View car] |
Member
Post nr. 112
Bucharest, Romania
11/80 323i 2.7i Motronic 1.3 |
| Tricord wrote: | | My version has breathing problems above 5000rpm, but it sure hauls under that rpm limit. I reckon I have steeper power and torque curves, but they plummet at 5000rpm instead of the usual 6000. I think I must be getting about 160HP at the crank, but no time or money to put the car on a dyno and find out the details.. |
the breathing probs arent direct related to the small intake ports the the 200 style head has? and the matched manifold? |
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| imaradiostar |
Posted
Tuesday, Mar 14th 5:57am [Edit] [Quote] [IMS] [View car] |
Member
Post nr. 673
Nashville, TN
81 323i, 82 525i, 85 524td, 90 535i |
| Gabi_323i wrote: | | Tricord wrote: | | My version has breathing problems above 5000rpm, but it sure hauls under that rpm limit. I reckon I have steeper power and torque curves, but they plummet at 5000rpm instead of the usual 6000. I think I must be getting about 160HP at the crank, but no time or money to put the car on a dyno and find out the details.. |
the breathing probs arent direct related to the small intake ports the the 200 style head has? and the matched manifold? |
At lower rpm the ports flow fine- they are well shaped for moderate flow and lower displacement like the 2.3 engine. When you reach higher rpm the velocity in the intake and ports is too high and you stop making power- it doesn't necessarily mean the engine won't rev that high, it just isn't worth it because torque drops off substantially.
The cure is more cam lift/duration or better flowing ports...tuners of the era usually stuck with the stock displacement so running out of breath at higher rpm was less of an issue. It seems those of us with 2.7 conversions sacrifice high-end (and peak) power in the name of torque.
Jeff Beyer is using (IIRC) an M3 crank and 85mm bore, a 325i head and extrude-honed intake and modified CIS injection. His engine is right at 2.9 liters displacement. In the extrude-hone thread he says he seems to have cured his high-rpm problem using extrude-hone. He's worked hard to find the right combination of parts to cure his high-rpm problem.
jamie |
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| aussie323i |
Posted
Tuesday, Mar 14th 10:49pm [Edit] [Quote] [IMS] [View car] |
Member
Post nr. 471
australia
1979 323i |
actually in tri's case it's the 4 barrel solex carb and manifold he's running 
this is why power drops off at 5000rpm. |
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| imaradiostar |
Posted
Wednesday, Mar 15th 4:37am [Edit] [Quote] [IMS] [View car] |
Member
Post nr. 674
Nashville, TN
81 323i, 82 525i, 85 524td, 90 535i |
I think it's fair to say there's more than the carb as the limiting factor as plenty of non-carbed 2.7's run similarly.
jamie |
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| JJG323 |
Posted
Wednesday, Mar 15th 5:03am [Edit] [Quote] [IMS] [View car] |
Member
Post nr. 1145
Reading MA USA
1979 BMW 323i |
Yes. Jamie so far I am impressed by Jeff's build.
I am going with Jason's e36 m3 manifolds if I ever get the budget and the time. I do have the s50 crank now as well.
Dennis those numbers are quite repectable and
I think you car should be a fun car to drive.
| Madhatter wrote: | depending on your dyno (and just how competent the operator is), the loss figure is significantly higher than 16%, low 20's is a more realistic figure, more if you run an auto.
Compression ratio isnt going to produce large power increases, at best you are talking 1.5-2% as a maximum per full point increase in comp ratio. Its not as important as some people think. |
Matthatter..Yeah. Its not just CR..
The increase stroke and displacement is the where the power can be gotten from the m20.
But to do this you need the s50/s52 crank, custom rods and pistons.
I have heard that Pete Mchenry will ask you what CR you want on you 3.0 stroker that he will build you. Some MM strokers have CR in the 10.5:1 range.. and thats what I have. |
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| TJ |
Posted
Wednesday, Mar 15th 5:19am [Edit] [Quote] [IMS] [View car] |
Member
Post nr. 1
NY, USA
82 528e2i 84 320i/4 80 320i |
Hello, everyone. Those numbers are a bit surprising to me, huge torque but a relatively low power peak compared to the 325i. When you were on the dyno did you also get a measurement of A/F ratio by any chance?
I'm doing a swap in my '82 528e soon (not as cool as an e21 I know) with only a few differences. I have some lightweight pistons with .5mm overbore and I'm also going to keep the Motronic 1.0. I have a ROM programmer so I can make my own custom chip.
There is a Holley adjustable fuel pressure regulator for Buick V6s that fits on some BMWs. I may end up using it if 3.0bar isn't enough (it's only around $90). Have any of you other guys with 2.7 M20s needed bigger injectors or extra fuel pressure? |
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| Tricord |
Posted
Wednesday, Mar 15th 3:12pm [Edit] [Quote] [IMS] [View car] |
Administrator
Post nr. 931
Belgium, Europe
323i Baur |
As far as I'm concerned, I've built the stroker while spending as little money as possible. I used parts I had laying around (such as the solex carb instead of K-jet) and basically only bought a gasket set to assemble everything.
Of course my mix is sub-optimal. It's true, you can push the stroker all the way to 7000rpm without problems, but you've started to lose power at about 5500rpm already.
My problem is, any fix helping up the low rpm ceiling is going to cost. Be it intake or port work, agressive cam, or anything else. I just can't afford anything better.
And yes, a stock EU spec 325i engine will get my car to move faster on a track than my own eta conversion, but it would have cost more  Plus, for me, assembling the engine is half the fun, so dropping a 325i engine wasn't really an option.
The low end grunt on the eta engine is quite impressive though. A mild engine like mine would be absolutely ideal for a daily driver. Lots of torque, smooth driving, and acceleration right there if you want/need it. Too bad the conversion is illegal for a road car down here. |
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| aussie323i |
Posted
Wednesday, Mar 15th 4:27pm [Edit] [Quote] [IMS] [View car] |
Member
Post nr. 472
australia
1979 323i |
Hi tri
in my earlier post I wasn't having a dig at you about the carb more pointing out that while everyone was going on about efi related issues for your 5000RPM torque drop off- your 2.7 has a carb...
I actually think your buget track car is great and it would be better if a few people actually hurried up and built their strokers and got them out on the track like you have 
As for me- my cheapy stroker is gonna run L-Jet with some spliced in Big 6 parts... yes it's not optimal either, but it's cheap for me, is a system I understand and will still make reasonable power... and yes- much like everyone else's, mine's not gonna happen for some time because my fully reconditioned 2.3L only has 40,000km on it!
(I do have all the bits for my 2.7 at home sitting in my shed )
Back to the post subject... good job Dennis- I'm sure your car is great on the street and is pretty much exactly what I will aim for in my build when it happens- a nice streetable engine with plenty of torque. |
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